Historically, flow measurement through flumes or over weirs has been accomplished by carrying out manual measurements using a staff gauge. These manual measurements required management personnel or farmers to read water levels and look up the corresponding flow rate from a table. These manual measurements cannot be taken on a continuous basis, and this creates inaccuracies in the estimation of water flow. In addition, events, such as the change of water levels between manual measurements creates inaccuracies in the measurement. These inaccuracies result in the delivery of too much or too little flow volume in irrigation related applications.
Chart recorders, such as the Stevens Recorder, have also been used in the past. The chart recorder prints a running record of the water level on a paper chart. A stilling well and enclosure are required for the proper operation. These devices are mechanical and require considerable maintenance. In addition, the chart records are tedious to read and do not permit simple, quick flow evaluation.
Data logging instrumentation equipment can be adapted to record a continuous flow record but this equipment is complex and exceeds continuous flow recording requirements.